1. Field of the Invention
This invention relates to a fuel tank assembly for a motorcycle, and a method of assembling the fuel tank assembly. More particularly, a fuel tank is described in which the fuel pump can reliably suck in fuel when the fuel level is low and when the fuel level fluctuates extensively.
2. Background Art
A configuration of a motorcycle fuel tank is known which includes a fuel pump at the bottom of the fuel tank, the pump serving to suck in fuel from the bottom of the tank. This arrangement is disclosed in Japanese Patent Laid-Open No. Hei. 1-257686, entitled "Fuel Tank". In FIGS. 1 through 3 and 5 of the related art, a pair of right and left main frames 14, 14 extend rearwardly from the rear end of a cylindrical steering shaft 12 of the body frame 10. A fuel tank 50 is placed on the main frames 14, has a protrusion 52 formed at the bottom thereof, and extends downwardly through the main frames 14. The protrusion 52 has an opening 64 on its bottom, through which a fuel pump 62 and a filter 73 are inserted into the fuel tank 50. The opening 64 is closed by a cover plate 66.
In the foregoing background art the filter 73 may be exposed to air if the fuel tank 50 houses a small amount of fuel, and if the fuel level fluctuates extensively due to acceleration deceleration or a change in posture of the motorcycle. This result is undesirable because when air is sucked in via the exposed filter 73, the fuel pump 62 rotates idly and cannot reliably suck fuel in.
In order to improve the suction performance of the fuel pump, the suction resistance of the filter may be reduced by using a large filter 73. However, the larger the filter 73, the larger the opening 64 must be in order to allow insertion of the filter into the tank. In order to maintain the rigidity of the fuel tank 50 with such a large filter, either a peripheral edge of the large opening 64 must be reinforced, or the fuel tank 50 must be thickened. These modifications are undesirable because they increase the weight and cost of manufacture of the fuel tank.